Le Naturaliste

Sédiment du lac Saimaa (Finlande).

Dimensions: 55 x 32 µm.
Stries: radiantes 8 à 10 µm.
Stries doublement ponctuées avec 12 - 14 points à 10 µm.

Une caractéristique qui différencie D. finnica des espèces voisines est
la présence d'ouvertures dans la zone marginale ou apicale, comme décrit dans l'article référencé:

Masahiko Idei a & Hiromu Kobayasi
THE FINE STRUCTURE OF DIPLONEIS FINNICA WITH SPECIAL REFERENCE TO THE MARGINAL OPENINGS, Diatom Research, 4:1, 25-37

“One of the peculiar features of D. finnica are square openings located in the outer wall of the alveoli (Figs 8, 10, 15, 20, 27, 28, 35 arrows, 36) though apparently similar structures are to be seen at the poles of the valve in Naviculu pygmaeu Kiitz. (Schoeman & Archibald 1980, Figs 35, 37 without comment; Krammer & Lange-Bertalot 1986, figs 65-66). These openings are usually restricted to positions close to the margin of the valve in the median and polar regions. They are also clearly visible by LM (Figs 2, 5, 6), but neithercleve (1894), Hustedt (1937) nor Patrick & Reimer (1966) referred to them. The openings in the external wall of the alveoli are square, irrespective of the presence of areolae (Figs 20, 27, 36).”